Oftentimes, a sectional door of the type used in openings of residential garages, utility buildings, and the like will not be retracted into the fully open position. That is, when “open,” all the panels of the sectional door are not oriented in a substantially horizontal position with the result that the bottom panel hangs down into the door opening.
There are several reasons why a sectional door is not retracted into a fully open position, thereby allowing the bottom panel to hang down into the door opening. For example, the spring in the counterbalance system attached to the sectional door tends to distend over a period of time. Therefore, although the counterbalance system could have originally operated to hold the sectional door in fully open, substantially horizontal position, the distension of the spring prevents the counterbalance system from counteracting the force of gravity, and the bottom panel of the sectional door hangs down into the door opening.
Furthermore, when sectional doors are configured for low headroom operation, these sectional doors characteristically hang down into the door opening. For example, sectional doors must be configured for low headroom installations when the top of the opening is close to the ceiling of the residential garage or utility building. To fit in the confined space, the counterbalance system used for low headroom installations is located directly adjacent the top of the opening, and proximate the transitional portions of the tracks.
Like other counterbalance systems, the springs of the counterbalance systems used for low headroom operation are loaded as the sectional door moves into the fully closed position and unloaded as the sectional door opens. Therefore, the unloading of the spring produces forces which assist with the opening movement of the sectional doors. Normally, the spring would assist with opening of the sectional door to the fully open position where all of the panels are all substantially horizontal. However, in the counterbalance systems used for low headroom operation, the spring is capable of assisting with the opening of the sectional door only to heights below the fully open position.
The location of the counterbalance system used for low headroom operation proximate the transitional portions of the tracks prevents the opening of the sectional door to the fully open position. For example, as the sectional door is opening, the spring of the counterbalance system is predisposed to retract cables attached to the lower extremities of the bottom panels. That is, the spring functions to reeve as much length of the cables around cable storage drums as possible to assist with the opening of the sectional door. In this respect, the lower extremities of the bottom panels are pulled into a counterbalance point by the reeving of the cables.
Like other counterbalance systems, the counterbalance system used for low headroom operation effectively biases the lower extremities of the bottom panels into the counterbalance point. However, because of the location of the counterbalance system used for low headroom operation relative to the transitional track portions, the counterbalance point is along these transitional track portions. As such, the spring is capable of assisting with the opening of the sectional door only to heights below the fully open position, and the lower panel of a sectional door configured for low headroom operation hangs down into the door opening.
The decrease in the effective height of the door opening due to the position of the counterbalance point was not a problem when mostly automobiles were being parked in residential garages and utility buildings. However, more recently, there are an increasing number of tall vehicles owned by consumers, such as vans and sport utility vehicles. These taller vehicles require additional clearance, and may not fit within the opening if there is significant hang down. This problem is compounded when a driveway angles downwardly toward the opening. When the opening is below level, the angled orientation of the vehicles upon entering the door opening requires still additional clearance. Such additional clearance may be unavailable if the bottom panel hangs down into the door opening.
One solution to eliminate the above-discussed hang down and increase the effective height of the door opening is to provide powered mechanical operating systems that pull the sectional door past the counterbalance point. As such, even when the sectional door is configured for low headroom operation, these mechanical operating systems retract the sectional door away from the top of the opening. However, many of the mechanical operating systems will not hold the sectional door in the fully open position for extended periods of time, thereby allowing the lower panel to move back into a hang down position in the opening.
Because many of the mechanical operating systems will not maintain the sectional door in the fully open, substantially horizontal position, the user must reactivate the mechanical operating system to retract the sectional door to the fully open position before a tall vehicle can safely enter or exit the door opening. If the user forgets to reactivate the mechanical operating system, damage will occur to both the vehicle and the sectional door.
Another solution to eliminate the above-discussed hang down and increase the effective height of the door opening is to build residential garages and utility buildings with ceiling heights greater than nine feet. Such ceiling heights allow conventional counterbalance systems to be used. For example, conventional counterbalance systems require the cable storage drums to be positioned at a height greater than the horizontal portions of the tracks. Such positioning permits the conventional counterbalance systems to locate the counterbalance point such that the sectional door is raised as high as possible in the door opening. These conventional counterbalance systems require at least thirteen to fourteen inches between the top of the opening and the ceiling to permit proper mounting. Therefore, a disadvantage of these conventional counterbalance systems is the inability to use such systems for low headroom operation in a preexisting structure where the top of the opening is close to the ceiling.
Consequently, the use of conventional counterbalance systems may not be possible in pre-existing residential garages and utility buildings. In fact, use of conventional counterbalance systems may also not be possible in new construction. For example, construction parameters frequently dictate a lower ceiling height, or the use of beams that do not provide the necessary headroom for the use of conventional counterbalance systems.
In an attempt to accommodate structures having minimal headroom, efforts have been made to modify conventional counterbalance systems. For example, one alternative is to move the cable storage drums laterally outboard of the tracks, and lowered to a point that the drive tube and brackets supporting the drive tube just permit clearance with the opening. However, such a configuration has serious limitations. The cables used in such a counterbalance system may bind due to the outward force applied during operation. Furthermore, even though this modified conventional counterbalance system reduces the necessary headroom from thirteen or fourteen inches to about twelve inches, the space required on either side of the tracks is increased, which may produce a problem in some instances.
Another alternative is a reversion to the use of one-piece door systems. These one-piece door systems, which may or may not employ tracks, normally pivot the door about a point approximately vertically medial of the door opening. One-piece door systems have not achieved substantial acceptance due to one or more of a combination of disadvantages. These systems require a substantial assured clearance either inside or outside the door any time it is opened or closed, depending on whether the door swings inwardly or outwardly. Furthermore, these systems require additional side clearance to accommodate the pivoting mechanism and counterbalance system thereof. Moreover, one-piece door systems cannot be packed, shipped, transported, or installed easily.
Yet another alternative contemplates the movement of the entire counterbalance system to the rear of the horizontal sections of the tracks. That is, the counterbalance system will be positioned proximate the extremities of the horizontal sections where the top panel of the sectional door reposes when the sectional door is opened. In such counterbalance systems, it is necessary to specially route the cables from the cable storage drums. For example, these cables are routed horizontally from the counterbalance system to the door frame, and using pulleys, are routed vertically to the lower extremities of the bottom panel. Such counterbalance systems have proven to be costly, and introduce an unsightly mechanism located centrally of the residential garage or utility building. As such, the springs of the counterbalance system are totally exposed to the interior of the garage, rather than being adjacent the opening where a person standing inside the garage may be exposed to the possibility of injury. Further, such systems often result in a geometry where the bottom panel nevertheless hangs down into the door opening when the door is in the open horizontal position.
Consequently, there is a need for a method and apparatus for positioning a sectional door above the door opening in the fully open position when the residential building or utility building in which the sectional door is located has minimal headroom clearance.